Harper hit 2 home runs in this game, his team was up by four. There is a time and a place to express your frustration with a GIDP, but that is certainly not the time.
I have no sympathy for Harper losing control of his emotions in that situation. Totally different than GIDPing when your team is behind or when you've had a rough night.
Right, he shouldn't have tossed the helmet, not the proper response. But I don't think tossing him was the proper response either